diff options
author | Suraj Jitindar Singh <sjitindarsingh@gmail.com> | 2018-10-08 16:31:07 +1100 |
---|---|---|
committer | Michael Ellerman <mpe@ellerman.id.au> | 2018-10-09 16:04:27 +1100 |
commit | fd10be257312b5d883f89d62d691443e95678fdd (patch) | |
tree | 5d1d4488a0e2a9379cfd1aa57758bba9e766d0a2 /arch/powerpc/kvm/book3s_hv_nested.c | |
parent | 4bad77799fede9d95abaf499fff385608ee14877 (diff) | |
download | linux-fd10be257312b5d883f89d62d691443e95678fdd.tar.bz2 |
KVM: PPC: Book3S HV: Handle page fault for a nested guest
Consider a normal (L1) guest running under the main hypervisor (L0),
and then a nested guest (L2) running under the L1 guest which is acting
as a nested hypervisor. L0 has page tables to map the address space for
L1 providing the translation from L1 real address -> L0 real address;
L1
|
| (L1 -> L0)
|
----> L0
There are also page tables in L1 used to map the address space for L2
providing the translation from L2 real address -> L1 read address. Since
the hardware can only walk a single level of page table, we need to
maintain in L0 a "shadow_pgtable" for L2 which provides the translation
from L2 real address -> L0 real address. Which looks like;
L2 L2
| |
| (L2 -> L1) |
| |
----> L1 | (L2 -> L0)
| |
| (L1 -> L0) |
| |
----> L0 --------> L0
When a page fault occurs while running a nested (L2) guest we need to
insert a pte into this "shadow_pgtable" for the L2 -> L0 mapping. To
do this we need to:
1. Walk the pgtable in L1 memory to find the L2 -> L1 mapping, and
provide a page fault to L1 if this mapping doesn't exist.
2. Use our L1 -> L0 pgtable to convert this L1 address to an L0 address,
or try to insert a pte for that mapping if it doesn't exist.
3. Now we have a L2 -> L0 mapping, insert this into our shadow_pgtable
Once this mapping exists we can take rc faults when hardware is unable
to automatically set the reference and change bits in the pte. On these
we need to:
1. Check the rc bits on the L2 -> L1 pte match, and otherwise reflect
the fault down to L1.
2. Set the rc bits in the L1 -> L0 pte which corresponds to the same
host page.
3. Set the rc bits in the L2 -> L0 pte.
As we reuse a large number of functions in book3s_64_mmu_radix.c for
this we also needed to refactor a number of these functions to take
an lpid parameter so that the correct lpid is used for tlb invalidations.
The functionality however has remained the same.
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/kvm/book3s_hv_nested.c')
-rw-r--r-- | arch/powerpc/kvm/book3s_hv_nested.c | 332 |
1 files changed, 329 insertions, 3 deletions
diff --git a/arch/powerpc/kvm/book3s_hv_nested.c b/arch/powerpc/kvm/book3s_hv_nested.c index 5b9fd7c8d931..21a210c134af 100644 --- a/arch/powerpc/kvm/book3s_hv_nested.c +++ b/arch/powerpc/kvm/book3s_hv_nested.c @@ -12,9 +12,12 @@ #include <linux/kvm_host.h> #include <asm/kvm_ppc.h> +#include <asm/kvm_book3s.h> #include <asm/mmu.h> #include <asm/pgtable.h> #include <asm/pgalloc.h> +#include <asm/pte-walk.h> +#include <asm/reg.h> static struct patb_entry *pseries_partition_tb; @@ -403,10 +406,20 @@ struct kvm_nested_guest *kvmhv_alloc_nested(struct kvm *kvm, unsigned int lpid) */ static void kvmhv_release_nested(struct kvm_nested_guest *gp) { + struct kvm *kvm = gp->l1_host; + + if (gp->shadow_pgtable) { + /* + * No vcpu is using this struct and no call to + * kvmhv_get_nested can find this struct, + * so we don't need to hold kvm->mmu_lock. + */ + kvmppc_free_pgtable_radix(kvm, gp->shadow_pgtable, + gp->shadow_lpid); + pgd_free(kvm->mm, gp->shadow_pgtable); + } kvmhv_set_ptbl_entry(gp->shadow_lpid, 0, 0); kvmppc_free_lpid(gp->shadow_lpid); - if (gp->shadow_pgtable) - pgd_free(gp->l1_host->mm, gp->shadow_pgtable); kfree(gp); } @@ -466,6 +479,12 @@ void kvmhv_release_all_nested(struct kvm *kvm) /* caller must hold gp->tlb_lock */ void kvmhv_flush_nested(struct kvm_nested_guest *gp) { + struct kvm *kvm = gp->l1_host; + + spin_lock(&kvm->mmu_lock); + kvmppc_free_pgtable_radix(kvm, gp->shadow_pgtable, gp->shadow_lpid); + spin_unlock(&kvm->mmu_lock); + radix__flush_tlb_lpid(gp->shadow_lpid); kvmhv_update_ptbl_cache(gp); if (gp->l1_gr_to_hr == 0) kvmhv_remove_nested(gp); @@ -525,7 +544,314 @@ void kvmhv_put_nested(struct kvm_nested_guest *gp) kvmhv_release_nested(gp); } -long kvmhv_nested_page_fault(struct kvm_vcpu *vcpu) +static bool kvmhv_invalidate_shadow_pte(struct kvm_vcpu *vcpu, + struct kvm_nested_guest *gp, + long gpa, int *shift_ret) +{ + struct kvm *kvm = vcpu->kvm; + bool ret = false; + pte_t *ptep; + int shift; + + spin_lock(&kvm->mmu_lock); + ptep = __find_linux_pte(gp->shadow_pgtable, gpa, NULL, &shift); + if (!shift) + shift = PAGE_SHIFT; + if (ptep && pte_present(*ptep)) { + kvmppc_unmap_pte(kvm, ptep, gpa, shift, NULL, gp->shadow_lpid); + ret = true; + } + spin_unlock(&kvm->mmu_lock); + + if (shift_ret) + *shift_ret = shift; + return ret; +} + +/* Used to convert a nested guest real address to a L1 guest real address */ +static int kvmhv_translate_addr_nested(struct kvm_vcpu *vcpu, + struct kvm_nested_guest *gp, + unsigned long n_gpa, unsigned long dsisr, + struct kvmppc_pte *gpte_p) { + u64 fault_addr, flags = dsisr & DSISR_ISSTORE; + int ret; + + ret = kvmppc_mmu_walk_radix_tree(vcpu, n_gpa, gpte_p, gp->l1_gr_to_hr, + &fault_addr); + + if (ret) { + /* We didn't find a pte */ + if (ret == -EINVAL) { + /* Unsupported mmu config */ + flags |= DSISR_UNSUPP_MMU; + } else if (ret == -ENOENT) { + /* No translation found */ + flags |= DSISR_NOHPTE; + } else if (ret == -EFAULT) { + /* Couldn't access L1 real address */ + flags |= DSISR_PRTABLE_FAULT; + vcpu->arch.fault_gpa = fault_addr; + } else { + /* Unknown error */ + return ret; + } + goto forward_to_l1; + } else { + /* We found a pte -> check permissions */ + if (dsisr & DSISR_ISSTORE) { + /* Can we write? */ + if (!gpte_p->may_write) { + flags |= DSISR_PROTFAULT; + goto forward_to_l1; + } + } else if (vcpu->arch.trap == BOOK3S_INTERRUPT_H_INST_STORAGE) { + /* Can we execute? */ + if (!gpte_p->may_execute) { + flags |= SRR1_ISI_N_OR_G; + goto forward_to_l1; + } + } else { + /* Can we read? */ + if (!gpte_p->may_read && !gpte_p->may_write) { + flags |= DSISR_PROTFAULT; + goto forward_to_l1; + } + } + } + + return 0; + +forward_to_l1: + vcpu->arch.fault_dsisr = flags; + if (vcpu->arch.trap == BOOK3S_INTERRUPT_H_INST_STORAGE) { + vcpu->arch.shregs.msr &= ~0x783f0000ul; + vcpu->arch.shregs.msr |= flags; + } return RESUME_HOST; } + +static long kvmhv_handle_nested_set_rc(struct kvm_vcpu *vcpu, + struct kvm_nested_guest *gp, + unsigned long n_gpa, + struct kvmppc_pte gpte, + unsigned long dsisr) +{ + struct kvm *kvm = vcpu->kvm; + bool writing = !!(dsisr & DSISR_ISSTORE); + u64 pgflags; + bool ret; + + /* Are the rc bits set in the L1 partition scoped pte? */ + pgflags = _PAGE_ACCESSED; + if (writing) + pgflags |= _PAGE_DIRTY; + if (pgflags & ~gpte.rc) + return RESUME_HOST; + + spin_lock(&kvm->mmu_lock); + /* Set the rc bit in the pte of our (L0) pgtable for the L1 guest */ + ret = kvmppc_hv_handle_set_rc(kvm, kvm->arch.pgtable, writing, + gpte.raddr, kvm->arch.lpid); + spin_unlock(&kvm->mmu_lock); + if (!ret) + return -EINVAL; + + /* Set the rc bit in the pte of the shadow_pgtable for the nest guest */ + ret = kvmppc_hv_handle_set_rc(kvm, gp->shadow_pgtable, writing, n_gpa, + gp->shadow_lpid); + if (!ret) + return -EINVAL; + return 0; +} + +static inline int kvmppc_radix_level_to_shift(int level) +{ + switch (level) { + case 2: + return PUD_SHIFT; + case 1: + return PMD_SHIFT; + default: + return PAGE_SHIFT; + } +} + +static inline int kvmppc_radix_shift_to_level(int shift) +{ + if (shift == PUD_SHIFT) + return 2; + if (shift == PMD_SHIFT) + return 1; + if (shift == PAGE_SHIFT) + return 0; + WARN_ON_ONCE(1); + return 0; +} + +/* called with gp->tlb_lock held */ +static long int __kvmhv_nested_page_fault(struct kvm_vcpu *vcpu, + struct kvm_nested_guest *gp) +{ + struct kvm *kvm = vcpu->kvm; + struct kvm_memory_slot *memslot; + struct kvmppc_pte gpte; + pte_t pte, *pte_p; + unsigned long mmu_seq; + unsigned long dsisr = vcpu->arch.fault_dsisr; + unsigned long ea = vcpu->arch.fault_dar; + unsigned long n_gpa, gpa, gfn, perm = 0UL; + unsigned int shift, l1_shift, level; + bool writing = !!(dsisr & DSISR_ISSTORE); + bool kvm_ro = false; + long int ret; + + if (!gp->l1_gr_to_hr) { + kvmhv_update_ptbl_cache(gp); + if (!gp->l1_gr_to_hr) + return RESUME_HOST; + } + + /* Convert the nested guest real address into a L1 guest real address */ + + n_gpa = vcpu->arch.fault_gpa & ~0xF000000000000FFFULL; + if (!(dsisr & DSISR_PRTABLE_FAULT)) + n_gpa |= ea & 0xFFF; + ret = kvmhv_translate_addr_nested(vcpu, gp, n_gpa, dsisr, &gpte); + + /* + * If the hardware found a translation but we don't now have a usable + * translation in the l1 partition-scoped tree, remove the shadow pte + * and let the guest retry. + */ + if (ret == RESUME_HOST && + (dsisr & (DSISR_PROTFAULT | DSISR_BADACCESS | DSISR_NOEXEC_OR_G | + DSISR_BAD_COPYPASTE))) + goto inval; + if (ret) + return ret; + + /* Failed to set the reference/change bits */ + if (dsisr & DSISR_SET_RC) { + ret = kvmhv_handle_nested_set_rc(vcpu, gp, n_gpa, gpte, dsisr); + if (ret == RESUME_HOST) + return ret; + if (ret) + goto inval; + dsisr &= ~DSISR_SET_RC; + if (!(dsisr & (DSISR_BAD_FAULT_64S | DSISR_NOHPTE | + DSISR_PROTFAULT))) + return RESUME_GUEST; + } + + /* + * We took an HISI or HDSI while we were running a nested guest which + * means we have no partition scoped translation for that. This means + * we need to insert a pte for the mapping into our shadow_pgtable. + */ + + l1_shift = gpte.page_shift; + if (l1_shift < PAGE_SHIFT) { + /* We don't support l1 using a page size smaller than our own */ + pr_err("KVM: L1 guest page shift (%d) less than our own (%d)\n", + l1_shift, PAGE_SHIFT); + return -EINVAL; + } + gpa = gpte.raddr; + gfn = gpa >> PAGE_SHIFT; + + /* 1. Get the corresponding host memslot */ + + memslot = gfn_to_memslot(kvm, gfn); + if (!memslot || (memslot->flags & KVM_MEMSLOT_INVALID)) { + if (dsisr & (DSISR_PRTABLE_FAULT | DSISR_BADACCESS)) { + /* unusual error -> reflect to the guest as a DSI */ + kvmppc_core_queue_data_storage(vcpu, ea, dsisr); + return RESUME_GUEST; + } + /* passthrough of emulated MMIO case... */ + pr_err("emulated MMIO passthrough?\n"); + return -EINVAL; + } + if (memslot->flags & KVM_MEM_READONLY) { + if (writing) { + /* Give the guest a DSI */ + kvmppc_core_queue_data_storage(vcpu, ea, + DSISR_ISSTORE | DSISR_PROTFAULT); + return RESUME_GUEST; + } + kvm_ro = true; + } + + /* 2. Find the host pte for this L1 guest real address */ + + /* Used to check for invalidations in progress */ + mmu_seq = kvm->mmu_notifier_seq; + smp_rmb(); + + /* See if can find translation in our partition scoped tables for L1 */ + pte = __pte(0); + spin_lock(&kvm->mmu_lock); + pte_p = __find_linux_pte(kvm->arch.pgtable, gpa, NULL, &shift); + if (!shift) + shift = PAGE_SHIFT; + if (pte_p) + pte = *pte_p; + spin_unlock(&kvm->mmu_lock); + + if (!pte_present(pte) || (writing && !(pte_val(pte) & _PAGE_WRITE))) { + /* No suitable pte found -> try to insert a mapping */ + ret = kvmppc_book3s_instantiate_page(vcpu, gpa, memslot, + writing, kvm_ro, &pte, &level); + if (ret == -EAGAIN) + return RESUME_GUEST; + else if (ret) + return ret; + shift = kvmppc_radix_level_to_shift(level); + } + + /* 3. Compute the pte we need to insert for nest_gpa -> host r_addr */ + + /* The permissions is the combination of the host and l1 guest ptes */ + perm |= gpte.may_read ? 0UL : _PAGE_READ; + perm |= gpte.may_write ? 0UL : _PAGE_WRITE; + perm |= gpte.may_execute ? 0UL : _PAGE_EXEC; + pte = __pte(pte_val(pte) & ~perm); + + /* What size pte can we insert? */ + if (shift > l1_shift) { + u64 mask; + unsigned int actual_shift = PAGE_SHIFT; + if (PMD_SHIFT < l1_shift) + actual_shift = PMD_SHIFT; + mask = (1UL << shift) - (1UL << actual_shift); + pte = __pte(pte_val(pte) | (gpa & mask)); + shift = actual_shift; + } + level = kvmppc_radix_shift_to_level(shift); + n_gpa &= ~((1UL << shift) - 1); + + /* 4. Insert the pte into our shadow_pgtable */ + + ret = kvmppc_create_pte(kvm, gp->shadow_pgtable, pte, n_gpa, level, + mmu_seq, gp->shadow_lpid); + if (ret == -EAGAIN) + ret = RESUME_GUEST; /* Let the guest try again */ + + return ret; + + inval: + kvmhv_invalidate_shadow_pte(vcpu, gp, n_gpa, NULL); + return RESUME_GUEST; +} + +long int kvmhv_nested_page_fault(struct kvm_vcpu *vcpu) +{ + struct kvm_nested_guest *gp = vcpu->arch.nested; + long int ret; + + mutex_lock(&gp->tlb_lock); + ret = __kvmhv_nested_page_fault(vcpu, gp); + mutex_unlock(&gp->tlb_lock); + return ret; +} |